Removal and recovery of toxic nanosized Cerium Oxide using eco-friendly Iron Oxide Nanoparticles

• Eco-friendly IONPs were synthesized through solvothermal method. • IONPs show very high removal efficiency for CeO₂ NPs i.e. 688 mg/g. • Removal was >90% in all synthetic and real water samples. • >80% recovery of CeO₂ NPs through sonication confirms reusability of IONPs. Increasing applications of metal oxide nanoparticles and their release in the natural environment is a serious concern due to their toxic nature. Therefore, it is essential to have eco-friendly solutions for the remediation of toxic metal oxides in an aqueous environment. In the present study, eco-friendly Iron Oxide Nanoparticles (IONPs) are synthesized using solvothermal technique and successfully characterized using scanning and transmission electron microscopy (SEM and TEM respectively) and powder X-Ray diffraction (PXRD). These IONPs were further utilized for the remediation of toxic metal oxide nanoparticle, i.e., CeO₂. Sorption experiments were also performed in complex aqueous solutions and real water samples to check its applicability in the natural environment. Reusability study was performed to show cost-effectiveness. Results show that these 200 nm-sized spherical IONPs, as revealed by SEM and TEM analysis, were magnetite (Fe₃O₄) and contained short-range crystallinity as confirmed from XRD spectra. Sorption experiments show that the composite follows the pseudo-second-order kinetic model. Further R²>0.99 for Langmuir sorption isotherm suggests chemisorption as probable removal mechanism with monolayer sorption of CeO₂ NPs on IONP. More than 80% recovery of adsorbed CeO₂ NPs through ultrasonication and magnetic separation of reaction precipitate confirms reusability of IONPs. Obtained removal % of CeO₂ in various synthetic and real water samples was>90% signifying that IONPs are candidate adsorbent for the removal and recovery of toxic metal oxide nanoparticles from contaminated environmental water samples.     

Dibutyl phthalate adsorption characteristics using three common substrates in aqueous solutions

• DBP adsorption was tested using three kinds of substrates in constructed wetlands. • The DBP adsorption capacity followed the order: steel slag>gravel>shell sand. • High temperatures increased the DBP adsorption capacity in the substrates. • DOM consistently inhibited the DBP adsorption onto steel slag and gravel. In recent years, the presence and adverse impacts of phthalic acid esters in aquatic environments have gained increasing attention. This work investigated the adsorption behavior of a typical phthalic acid ester, dibutyl phthalate (DBP), onto steel slag, gravel, and shell sand (substrates commonly used in constructed wetlands). The influence of dissolved organic matter (DOM) on DBP adsorption was investigated using humic acid as a proxy for DOM. The results demonstrated that the adsorption of DBP to three substrates reached equilibrium within 96 h, and the adsorption kinetics were well fitted by a pseudo-second-order model. The DBP adsorption isotherms were best fitted by the Langmuir adsorption model. The DBP adsorption capacity decreased in the order of steel slag>gravel>shell sand, with values of 656 mg/kg, 598 mg/kg, and 6.62 mg/kg at 25°C, respectively. DBP adsorbed to the surface of all substrates in a monolayer via an endothermic process. The DBP adsorption capacities of steel slag and gravel decreased as the DOM content increased. The DBP adsorption mechanisms to steel slag and gravel mainly involved the surface coordination of DBP with –OH or –COOH groups and electrostatic interactions. The results of this work suggest that steel slag and gravel may be ideal substrates for use in constructed wetlands to treat wastewater polluted with DBP.     

Ammonia and phosphorus removal from agricultural runoff using cash crop waste-derived biochars

• Orange tree residuals biochar had a better ability to adsorb ammonia. • Modified tea tree residuals biochar had a stronger ability to remove phosphorus. • Partially-modified biochar could remove ammonia and phosphorus at the same time. • The real runoff experiment showed an ammonia nitrogen removal rate of about 80%. • The removal rate of total phosphorus in real runoff experiment was about 95%. Adsorption of biochars (BC) produced from cash crop residuals is an economical and practical technology for removing nutrients from agricultural runoff. In this study, BC made of orange tree trunks and tea tree twigs from the Laoguanhe Basin were produced and modified by aluminum chloride (Al-modified) and ferric sulfate solutions (Fe-modified) under various pyrolysis temperatures (200°C–600°C) and residence times (2–5 h). All produced and modified BC were further analyzed for their abilities to adsorb ammonia and phosphorus with initial concentrations of 10–40 mg/L and 4–12 mg/L, respectively. Fe-modified Tea Tree BC 2h/400°C showed the highest phosphorus adsorption capacity of 0.56 mg/g. Al-modified Orange Tree BC 3h/500°C showed the best performance for ammonia removal with an adsorption capacity of 1.72 mg/g. FTIR characterization showed that P = O bonds were formed after the adsorption of phosphorus by modified BC, N-H bonds were formed after ammonia adsorption. XPS analysis revealed that the key process of ammonia adsorption was the ion exchange between K⁺ and NH₄⁺. Phosphorus adsorption was related to oxidation and interaction between PO₄^3– and Fe³⁺. According to XRD results, ammonia was found in the form of potassium amide, while phosphorus was found in the form of iron hydrogen phosphates. The sorption isotherms showed that the Freundlich equation fits better for phosphorus adsorption, while the Langmuir equation fits better for ammonia adsorption. The simulated runoff infiltration experiment showed that 97.3% of ammonia was removed by Al-modified Orange tree BC 3h/500°C, and 92.9% of phosphorus was removed by Fe-modified Tea tree BC 2h/400°C.     

MIEX树脂在饮用水预处理中的应用研究

本文采用一种新型的MIEX磁性离子交换树脂对某水厂原水进行预处理,考察了MIEX树脂用量与后续混凝工艺对原水的浊度、有机物、无机阴离子的去除效果。结果表明,MIEX技术可有效地去除原水中的有机物,对UV254和CODMn的去除率分别稳定在90%和59%。MIEX树脂对无机阴离子也有很好的去除效果,对SO24-的去除率一般为80%以上,NO3-为50%以上。但MIEX树脂对低浊水的去浊效果一般,同时MIEX预处理可以有效强化混凝沉淀对有机物的去除。     

Removal of uranium(VI) from aqueous solutions and nuclear industry effluents using humic acid-immobilized zirconium-pillared clay

Removal of uranium [U(VI)] from aqueous solutions with humic acid-immobilized zirconium-pillared clay (HA-Zr-PILC) was investigated using a batch adsorption technique. The adsorbent was characterized using XRD, FTIR, SEM, TG/DTG, surface area analyzer and potentiometric titration. The effects of pH, contact time, initial concentration, adsorbent dose, and adsorption isotherm on the removal process were evaluated. A maximum removal of 97.6 ± 2.1 and 94.7 ± 3.3% was observed for an initial concentration of 50 and 100 mg L⁻¹, respectively at pH 6.0 and an adsorbent dose of 2.0 g L⁻¹. Equilibrium was achieved in approximately 180 min. The mechanism for the removal of U(VI) ions by HA-Zr-PILC was based on an ion exchange reaction. The experimental kinetic and isotherm data were analyzed using a second-order kinetic equation and Langmuir isotherm model, respectively. The monolayer adsorption capacity for U(VI) removal was found to be 132.68 ± 5.04 mg g⁻¹. An increase of temperature of the medium caused an increase in metal adsorption. Complete removal (≅100%) of U(VI) from 1.0 L of a simulated nuclear industry effluent sample containing 10.0 mg U(VI) ions was possible with 1.5 g of HA-Zr-PILC. The adsorbent was suitable for repeated use (over 4 cycles) without any noticeable loss of capacity.     

B,N和Ce共掺杂TiO_2催化剂光催化活性研究

采用溶胶-凝胶法制备出B,N和Ce共掺杂TiO2光催化剂,并用XRD、SEM等表征了其结构特征。以酸性大红染料溶液的光催化降解为探针反应,考察了制备条件对共掺杂TiO2催化剂活性的影响。结果表明,在400℃,当B,N和Ce的原子比为1∶2∶0.1,焙烧3 h时,光催化剂活性最大,大红染料的降解率达到98%。     

Equilibrium study and kinetics of Cu removal from water by zeolite prepared from oil shale ash

Engineered zeolite was produced from oil shale ash by reaction with sodium hydroxide in a closed vessel reactor. This adsorbent was used for removal of copper ions from aqueous solution. The maximum adsorption capacity was 504.6 mg Cu²⁺/g zeolite. Kinetic studies showed that the rate of adsorption of copper is increased with increasing the solution pH and temperature, quantity of the zeolite and agitation speed. The kinetic data were fitted to homogeneous micropore model and found that the mass transfer coefficient and diffusivity of the Cu²⁺ are directly affected by the kinetic parameters. The increase in solution concentration will decrease the mass transfer coefficient while diffusivity is increased.     

表面活性剂强化超滤法处理亚甲基蓝废水

采用无机陶瓷超滤膜和低浓度阴离子表面活性剂十二烷基苯磺酸钠(SDBS)处理亚甲基蓝(MB)模拟废水,考察了废水中SDBS、MB浓度及废水pH对超滤过程的影响.实验结果表明:SDBS浓度影响MB在最大吸收波长处的吸光度值;当废水中SDBS浓度为1.20 mmol/L(即25℃时的临界胶束浓度)、废水中MB浓度为1.00 mmol/L、废水pH为9.0时,超滤效果最好;在此条件下,透过液中SDBS浓度和MB浓度分别为0.06 mmoL/L和0.01 mmol/L,MB的截留率为99.2%,膜通量为309.6 L/(m~2·h).SDBS对MB超滤过程的强化机理主要为MB与SDBS形成结合体析出及SDBS胶束的增溶作用.     

污泥-谷壳吸附剂对混合染料吸附机理的研究

污泥和谷壳为原料制备了污泥-谷壳吸附剂（SCA）。采用SCA处理酸性大红和碱性嫩黄模拟混合染料废水。通过动力学分析、FTIR表征和SEM表征对SCA吸附混合染料的机理进行了研究。实验结果表明：在吸附温度25 ℃、混合溶液中酸性大红和碱性嫩黄的质量浓度均为100 mg/L、SCA加入量0.5 g/L、吸附时间400 min的条件下,酸性大红的吸附量为125 mg/g,碱性嫩黄的吸附量为170 mg/g;SCA对混合染料的吸附行为符合拟二级反应动力学方程,液膜扩散为吸附的主要控制过程。表征结果显示：SCA孔隙发达且丰富,以中孔和细密的微孔为主,说明SCA具有较高的吸附能力; SCA中包含C—H,C—OH,C—C,CC等主要官能团,SCA对混合染料的吸附为物理吸附。     

SO42-/SnO2 -Fe2O3-硅藻土固体酸催化剂的制备及其对染料废水的催化处理

以硅藻土为载体,采用溶胶-凝胶法引入金属氧化物SnO₂和Fe₂O₃,制备了二元氧化物复合型SO₄^2-/SnO₂-Fe₂O₃-硅藻土固体酸催化剂。利用该催化剂与H₂O₂构成非均相类Fenton试剂氧化体系,催化H₂O₂产生氧化能力极强的·OH,用于处理实际翠蓝废水和模拟亚甲基蓝废水。催化剂的最佳制备条件为：H₂SO₄溶液的浓度3 mol/L,浸渍时间2.0 h,焙烧温度550 ℃,焙烧时间3.5 h,焙烧方式为随炉升降温。实验结果表明：采用在最佳工艺条件下制得的催化剂,处理实际翠蓝废水COD去除率可达79.5%、脱色率达99.6%;处理模拟亚甲基蓝废水COD去除率可达83.1%、脱色率达99.6%。